Anthropogenic Radionuclides in the Estuarine Environment Near a Boiling Water Nuclear Reactor

Anastasia collecting samples in Barnegat Bay, New Jersey.

I. INTRODUCTION
I can never remember a time when I did not know and love New Jersey's Barnegat Bay. It is a treasured and fragile ecosystem. It shimmers in the sunrise and glimmers at sunset. It beckons me on expeditions to explore its islands and marshes and to learn about its many inhabitants.
Barnegat Bay is surrounded by sand dunes, thick marshlands, the magnificent Pine Barrens forest, and also some highly developed land. Many beautiful streams and creeks drain into the bay from the mainland, each with its own special character. The bay is home to an incredibly diverse wildlife population, and until recently, it had supported a thriving shellfish and fishing industry and provided untold hours of recreational pleasure to its visitors.
Because my mother is from New Jersey and spent her childhood in and around the Barnegat Bay, my four brothers and I were introduced to the bay when we were each but a few weeks old. We've spent summers there, and in our marine biology classes, or at our mother's side, we learned to treasure the bay. I sometimes believe that the bay's marshes and its mud have become part of me. (It certainly feels like the mud is ingrained in my skin when I come in from collecting samples.)This passion for the bay has inspired me to do scientific research in the Barnegat Bay's estuary. The project described here is my fifth year of work in the bay. Barnegat Bay is surrounded by one of the fastest-growing population areas in New Jersey. My first project in the bay was an examination of whether its water quality has changed with population growth. I collected 40 years of historical water-quality data, took current water samples during two seasons, and compared the current results to the historical data for 11 water-quality indicators. I concluded that the water quality in the estuary has declined in several significant respects.

Figure 1: Anastasia near the Oyster Creek Nuclear Generating Station.

In the second year of my research, I studied water quality and how it relates to the growth of gram-negative pathogen-indicator bacteria. I concluded that temperature, pH, nitrate-nitrogen, and dissolved oxygen affect bacteria growth in the bay, but salinity does not. During this time period, I applied for and received two U.S. Environmental Protection Agency grants to write an illustrated pamphlet on how to protect the bay. I distributed over 18,000 copies to realtors on Long Beach Island, the island that is the eastern border of the bay.

In 2004, I learned about the Oyster Creek Nuclear Generating Station, a nuclear reactor operating along Oyster Creek, which flows into the Barnegat Bay. I investigated the waters around the reactor and observed what seemed to be some dramatic differences between the creek leading into the reactor and the creek into which the reactor discharges water. In 2005, I began my research into the impact of the reactor by examining the microbial communities and water quality in the reactor's intake and discharge creeks and comparing them to a nearby control creek.

Last year, I studied species abundance and species diversity in the reactor's intake and discharge creeks compared to the nearby control creek. I studied the benthic, plankton, and biofouling communities while I continued to test water-quality parameters and study the microbial populations.

Figure 2: Anastasia collecting sediment.

This year, I did a spatial study of radioactivity in the waters near the reactor. My study examines anthropogenic radionuclides, which are the radionuclides that result from human activity. Most anthropogenic radionuclides are byproducts of weapons and nuclear reactor operations. The purpose of my project is to study anthropogenic radionuclides in the estuarine environment near the Oyster Creek Nuclear Generating Station to determine if there are higher levels of anthropogenic radionuclides in the aquatic sediment, water, and marsh near the reactor. I believe it is important to understand whether radionuclides are present in recreational waters, because it is no longer believed that there are safe levels of radionuclide exposure. According to the most recent report from the National Academy of Sciences, there is no known safe level of exposure. It reports that each exposure can produce a corresponding risk, and that the danger is greater for women and even greater for children (National Academy of Sciences 2006).

The hypothesis is that there are higher concentrations of anthropogenic radionuclides in the immediate vicinity of the reactor, especially in the reactor's discharge creek. Radionuclide concentrations will decline as distances from the reactor increase. Also, the area north of the reactor will have higher concentrations of anthropogenic radionuclides than the area south of the reactor, because the prevailing winds blow south to north.

A. The Oyster Creek Nuclear Generating Station The Oyster Creek Nuclear Generating Station, which became operational in 1969, is located in New Jersey's Barnegat Bay estuary. It is a 630-megawatt boiling-water reactor, one of 34 operating in the United States (List of Power Reactors 2006). It is almost equidistant from New York City and Philadelphia, about 60 miles from each city. The Oyster Creek Reactor sits on a 533-hectare site (1,316 acres) at the artificially constructed confluence of Forked River and Oyster Creek. The reactor is located in a fragile ecosystem with extensive freshwater and saltwater marshes, and is an area that has a large groundwater reserve (Oyster Creek Nuclear Generating Station 2007).

Figure 3: Sediment grabber filled with sediment sample..

Oyster Creek uses a "once-through" cooling system, drawing 4.5 billion liters (1.2 billion gallons) of water daily from Forked River, heating the water, and discharging it into Oyster Creek (O'Malley 2004). Before the reactor was built, Forked River and Oyster Creek were separate, and both flowed east into the Barnegat Bay. When the reactor was constructed, the creeks were dredged, widened, and connected at the reactor. Water is now pulled in from the intake creek, Forked River, which now flows westward from the bay to the reactor.Oyster Creek's operating license is currently up for renewal, and a major controversy has erupted about whether the license should be renewed. On December 18, 2007, the U.S. Atomic Safety and Licensing Board recommended that the U.S. Nuclear Regulatory Commission approve a 20-year extension to operate the reactor (Benson 2007). On January 3, 2008, New Jersey's Department of Environmental Protection granted a much-contested permit, determining that the plant meets federal requirements under the Coastal Zone Management Act of 1972 (DEP 2008). One aspect of the controversy is the anthropogenic radionuclides emitted by the Oyster Creek reactor.

B. Naturally Occurring and Anthropogenic Radionuclides
A radionuclide is a radioactive isotope of an element containing more neutrons than a stable isotope of the same element. The environment includes natural radionuclides, such as those people are exposed to when flying at high altitudes. Major sources of anthropogenic (human-produced) radionuclides are the nuclear industry, medical applications, and nuclear weapons testing (Collon 2004). There were no radionuclides before 1945 that did not naturally occur (Giuliani 2003). Anthropogenic radionuclides were introduced into the marine environment in the 1940s, when nuclear fission was first used in military activities (Aarkrog 1998). Although weapons testing was at its height in the 1960s, sources of radionuclides remain today, primarily from operation of nuclear plants (RADNET 2008).Radionuclides emit ionizing radiation, which can injure the body's deoxyribonucleic acid (DNA) (United Nations 2000). According to one of the nation's leading estuarine experts, radionuclide uptake by organisms in estuaries is a significant health concern because excessive radiation levels can lead to chromosomal irregularities, resulting in cancer and other problems (Kennish 2001). Exposure to anthropogenic radiation is a particularly important topic now as the search intensifies for alternatives to fossil fuel. Renewing licenses for older nuclear power plants is part of that debate, as there is a fear that older power plants emit unacceptable levels of radionuclides into the environment. For many years, scientists believed that exposure to low levels of anthropogenic radionuclides was without risk. That viewpoint is being revisited, and many scientists now believe that exposure to even low levels of anthropogenic radiation is much more dangerous than was once thought. In fact, the National Research Council report on the "Biological Effect of Ionizing Radiation" concluded in 2005 that even the smallest radiation dose could increase the risk for cancer (known as the "linear-no-threshold" model) (National Academy of Sciences 2006).

C. Radionuclides at the Oyster Creek Nuclear Reactor
Like all nuclear power plants, Oyster Creek releases anthropogenic radionuclides. Oyster Creek files annual reports with the U.S. Nuclear Regulatory Commission about the amount of radionuclides it releases. The reactor's reports do not track the pathways of these radionuclides as they move through the estuary. There has been a study of sediment pathways through the Barnegat Bay that monitored reactor-released radionuclides as the tracing mechanism (Olsen 1980). This author is unaware of any study of anthropogenic radionuclides in the many creeks near the reactor.Reports filed with the United States Nuclear Regulatory Commission show that the amount of radioactive discharges from Oyster Creek is consistently ranked in the top 10 of all of the nation's 103 operating nuclear reactors (Mangano 2007).

D. The 14 Radionuclides Focused On in This ProjectDuring my research, I read three important papers that tracked radioactivity from nuclear power plants (Mulholland and Olsen 1992; Donoghue 1989; Olsen 1980). Fourteen of the radionuclides studied in those papers were the gamma-emitters studied in this project. These radionuclides became the focus of this study because of their known relation to nuclear power plants. The 14 radionuclides are described below.

Americium-241 ( 241 Am). Americium-241 has a half-life of 432.7 years. Americium-241 tends to concentrate in muscle, bone marrow, and the liver. It can remain in the human body for many decades, increasing cancer risk (Radiation Protection 2007),

Barium-140 ( 140 Ba). Barium-140, a gamma- and beta-emitter, has a half-life of 12.8 days. It is a short-lived radionuclide, but it can make up about 10 percent of nuclear fission byproducts immediately after emission (Sastry 1966). In humans, barium-140 acts similarly to calcium, concentrating in bones (Environmental and Workplace 1995).

Beryllium-7 ( 7 Be). Beryllium-7 has a half-life of 53.3 days. It causes chronic beryllium disease, a disease characterized by nodule growth in the lungs, and lung cancer (Lang 1994).

Cerium-144 ( 144 Ce). Cerium-144 is an anthropogenic radionuclide with a half-life of 282 days. It constitutes a substantial portion of the radionuclides found in seawater; it tends to concentrate in phytoplankton, setting the stage for cerium-144 to move up the food chain (Rice and Willis 1959). It is absorbed in bone and is one of the more hazardous radionuclides (Richmond and London 1966).

Cesium-134 ( 134 Cs). Cesium-134 has a half-life of 2.07 years. The cesium-134 in sediment in the Barnegat Bay estuarine environment is primarily from the operations of the Oyster Creek Nuclear Reactor (Olsen 1980).

Cesium-137 ( 137 Cs). Cesium-137 is considered to be of substantial concern from a health viewpoint (Environmental and Workplace 1995). It has a half-life of over 30 years and is extremely toxic, even in small amounts. It is the most abundant radionuclide at most nuclear reactor locations (NCRP 2006). Biologically, cesium-137 is capable of targeting soft tissue, but similar to potassium, it concentrates in muscle tissue. The body eliminates cesium after about three months (Cesium 2005).

Cobalt-58 ( 58 Co) and Cobalt-60 ( 60 Co). Cobalt-58 has a half-life of 70.9 days, while cobalt-60 has a half-life of 5.27 years. Neither cobalt-58 nor cobalt-60 is a nuclear-fission product, so unlike cesium-137, they are not products of weapons testing (Cobalt 2006). Virtually all cobalt in the environment ends up in sediment or soil. In the body, cobalt targets primarily the liver, kidneys, and bones (Cobalt 2006). Cobalt-60 is listed as one of eight most dangerous radionuclides.

Iron-59 ( 59 Fe). Iron-59 has a physical half-life of 44.5 days. It rarely occurs alone but most likely is in a compound. It is used in medical studies to act as a tracer in blood tests (Radioisotope Information 2007).

Manganese-54 ( 54 Mn). Manganese-54 has a physical half-life of 312.5 days. The occurrence of manganese-54 in the Barnegat Bay estuary sediment primarily stems from low-level releases from the Oyster Creek plant (Olsen 1980). Its target areas are the liver, bones, and the gastrointestinal tract (Radioisotope Information 2007).

Niobium-94 ( 94 Nb). Niobium-94 has a half-life of 20,300 years (Niobium 2007).

Silver-110m ( 110m Ag). Silver 110m has a half-life of 249 days. Studies suggest that silver 110m concentrates in the liver and brain (Folsom and Young 1965).

Zinc-65 ( 65 Zn). Zinc-65 has a half-life of 243.9 days. It is a radioactive isotope of zinc. Zinc is an essential nutrient for algae and is well positioned to move up the food chain (Gutknecht 1965).

Zirconium-95 ( 95 Zr). Zirconium-95 is a radioactive isotope of zirconium. Zirconium-95 is a plentiful byproduct of the operation of nuclear power plants. It has a half-life of 29 years.

Figure 4: Map of sampling area & Figure 5: Inset map of sampling area in the immediate vicinity of the reactor.

II. MATERIALS, METHODS, AND PROCEDURES

Figure 6: Graph of Niobium-94 in water.

In this study, water, sediment, and marsh samples were collected in the Barnegat Bay estuary within 8 km north and 34 km south of the Oyster Creek Nuclear Generating Station and were analyzed for 50 gamma-emitting radionuclides.

A. Sampling Overview This was a spatial, not a temporal study. There were 42 sampling sites, divided into three sampling regions. One region was north (downwind) of the reactor; the second was the reactor's discharge creek, Oyster Creek; and the third was south of the Oyster Creek reactor. One hundred thirty-one water, aquatic sediment, and marsh samples were collected during a six-month period, from July through December. There were 42 water-sampling sites, from which 51 water samples were collected. Forty aquatic sediment samples were collected from 35 sampling sites. Forty marsh samples were collected from 34 marsh-sampling sites. At some sites, there was no marsh growing, so no sample could be taken. In some instances, sampling conditions precluded collecting sediment samples. Sampling locations and numbers are shown in Figure 4.

Figure 7: Scatterplot of Silver-110m by water distance.

B. Materials All materials are commercially available and included a Field Master Mighty Grab™ (sediment field grabber), 51 one-liter bottles with screw-on caps, 80 one-liter sampling containers with snap-on lids for collecting aquatic sediment and marsh samples, duct tape to seal all containers, and a serrated knife to facilitate collection of marsh samples.

C. Procedures for Water Samples A one-liter bottle was rinsed in water at the sampling site, capped, submerged to a depth of 0.5 meters and allowed to fill. The bottle was recapped while still underwater.

Figure 8: Scatterplot of Silver-110m by line distance.

D. Procedures for Marsh Samples

Figure 9: Graph of Silver-110m in water.

Marsh samples were collected from an area close to the water's edge, but with no part of the marsh growth submerged in the water. With the serrated knife, sediment from the marsh was cut and placed in the sampling container until the container was tightly filled.

Figure 10: Graph of total radiation for studied radionuclides in water.

E. Procedures for Aquatic Sediment Samples The Field Master Mighty Grab™ field grabber was submerged to the creek floor, pressed into the sediment and pulled to the surface. Sediment from the center of the sample (which had not made contact with the water as the grabber was pulled up) was transferred to the collection container, filling the container to the top.

Figure 11: Scatterplot of total naturally occurring radioactivity in water.

F. Laboratory Analysis All samples were packed in coolers with ice. The samples were shipped by overnight delivery to GEL Laboratories LLC in South Carolina, where they were analyzed using gamma spectroscopy analysis. Results were reported for 50 gamma-emitting radionuclides. Water results were in pCi/L, and sediment and marsh results were reported in pCi/g.

Figure 13: Graph of Cobalt-60 in sediment.

III. RESULTS AND FINDINGS A. Methods of Analysis

For analysis of the data, the data from each of the three regions—the southern region (the area south of the reactor), Oyster Creek (the discharge creek), and the northern region (the area north of the reactor)—were compared. To test for the statistical significance of the variations among the regions, analysis of variance (a = 0.05) was used. Individual contrasts within ANOVA were used to compare the three regions in individual pairs.

Figure 12: Graph of total naturally occurring radioactivity in water.

In addition to analysis of variance, the amount of radiation at each site was paired with its distance from the nuclear reactor, and Pearson's correlation coefficient was calculated, along with the significance of the correlation. Two distances were found for each site: the straight line distance (as-the-crow-flies) from the reactor, which is called the "line distance" in this discussion, and the approximate path water would travel from the reactor to the site, called the "water distance."
Of the 50 radionuclides that were analyzed, 10 of them are naturally occurring. Anthropogenic radionuclides were the primary interest. For the data analysis, the 14 anthropogenic radionuclides determined to be the most commonly used in radionuclide research involving nuclear power plants were studied. These are referred to as the "studied radionuclides" in this discussion. Also, the researcher briefly examined the data for the 26 other anthropogenic radionuclides, and those that appeared to have large differences were examined more closely.

Figure 14: Scatterplot of Cobalt-60 in sediment by line distance.

In addition to comparing individual radionuclides, several combinations of the sums of radioactivity were also compared: the total radioactivity of all 50 radionuclides, the total radioactivity of the 14 studied radionuclides, the total radioactivity of all 40 anthropogenic radionuclides, and the total radioactivity of the 10 naturally occurring radionuclides. Data points that were three standard deviations above or below the mean of the data for their respective regions were considered outliers. It is noted in the paper where the statistics exclude outliers.

Figure 15: Scatterplot of Cobalt-60 in sediment by water distance.

To ensure that time was not a confounding variable in the study, ANOVA, with the data grouped by test day, and Pearson's correlation, with days from July 1 by radionuclide readings, were performed on the data. None of the tests showed time as a variable.
On the graphs in this section, the southern region is Region 1 and the data points are in green; Oyster Creek is Region 2 and the data points are in orange; and the northern region is Region 3 and the data points are in blue.For the following charts, 0 pCi/L (or pCi/g) indicates that the average value was negative, but for interpretation this is read as zero radioactivity.

B. Water Data For the comparisons of the water data, two of the 14 studied radionuclides, niobium-94 and silver-110m, showed Oyster Creek significantly higher than the other two regions. For combinations of total radioactivity, the total of both the 14 studied radionuclides and the 10 naturally occurring radionuclides were significantly different among the regions. Two other anthropogenic radionuclides showed significant differences: cesium-136 and promethiuim-144.

Figure 16: Graph of total naturally occurring radioactivity in sediment.

The average radioactivity in Oyster Creek was higher than the other two regions for 12 other radionuclides, but the differences were not statistically significant. Those radionuclides were antimony-124, barium-140, beryllium-7, bismuth-212, cerium-139, cerium-141, cerium-144, cobalt-57, iron-59, niobium-95, ruthenium-106, and yttrium-88 ( indicates one of the 14 studied radionuclides). Also, Oyster Creek had higher average radioactivity for the anthropogenic radionuclides than the other two creeks.

C. Sediment Data
For the 14 studied radionuclides, Oyster Creek had significantly higher cobalt-60 concentrations in its aquatic sediment than the other creeks. For the combinations of total radioactivity, the only combination that showed significant differences among the regions was the radioactivity of the 10 naturally occurring radionuclides.For the other anthropogenic radionuclides, neodymium-147 showed significant differences between regions. The average radioactivity for 10 of the radionuclides was higher in Oyster Creek sediment than in the other regions, but the differences were not statistically significant. Those 10 radionuclides were antimony-124, antimony-125, barium-133, beryllium-7, cesium-136, europium-154, europium-155, iron-59, mercury-133, and sodium-22 ( indicates a studied radionuclide). Also, Oyster Creek had higher average radioactivity than the other regions for the 14 studied radionuclides and for all the anthropogenic radionuclides.

D. Marsh Data

Figure 17: Scatterplot of total naturally occurring radiation by water distance.

For the 14 studied radionuclides, only cobalt-58 was significantly higher in Oyster Creek than in the other two regions. For the combinations of total radioactivity, the only combination that showed significant differences was the radioactivity of the 10 naturally occurring radionuclides. For the other radionuclides, bismuth-212, europium-154, and sodium-22 showed Oyster Creek significantly higher than the other regions.The average radioactivity in Oyster Creek was higher than the other two regions for three other radionuclides, but the differences were not statistically significant. Those radionuclides were americium-241, cobalt-57, and promethium-146 ( indicates one of the 14 studied radionuclides). Also, Oyster Creek had higher average radioactivity than the other two creeks for the 14 studied radionuclides and all anthropogenic radionuclides.

IV. DISCUSSION AND CONCLUSIONS Based on the data collected in this study, my hypothesis is supported that there are higher levels of anthropogenic radionuclides closer to the reactor. The average values of many anthropogenic radionuclides are higher in the water, sediment, and marsh of Oyster Creek than in areas north or south of the reactor. Several of these differences are statistically significant. Also, many correlations of distance and radioactivity indicate a negative association, supporting the hypothesis that increasing distance from the reactor leads to lower levels of radionuclides.

Figure 18: Scatterplot of total naturally occurring radiation by line distance.

My hypothesis that the northern region has higher levels of radioactivity than the southern region, however, is not supported. While there are radionuclides for which the northern region has a higher average than the southern region, none of these differences is statistically significant.
Higher radioactivity in the vicinity of the reactor potentially affects both the human population and the environment. Since ionizing radiation can cause mutations in the DNA of all living cells, higher radioactivity increases the risk for all organisms exposed. Several of the isotopes found to be higher in Oyster Creek are known to be particularly hazardous, such as cobalt-60.
One interesting finding is that the levels of naturally occurring radionuclides are much higher in the southern region than in either the northern region or Oyster Creek. Oyster Creek, in fact, has the lowest levels of naturally occurring radioactivity for water, aquatic sediment, and marsh. It would seem that the geology of the southern region contains more radionuclides than the other regions. While this seems unlikely to affect the results of this study, given that the naturally occurring radionuclides were separated from the anthropogenic ones for the analysis, I think it is a noteworthy finding.One way to improve this project would be to increase the sample size. The variation in the data is very large compared to the number of samples, so it is hard to distinguish outliers, and it is likely that true differences in means do not show up as statistically significant because the spread of the data is too large compared to the differences in the means. This has the potential to alter the results and could affect not only the tests comparing means, but also correlations.

Figure 19: Graph of Cobalt-58 in marsh.

The sample size (131 total samples), given the variation in the data and the fact that fewer than expected radionuclides showed significant differences, limits the scope of the conclusions that can be drawn from this study. The findings do show that it is very likely that there are higher levels of anthropogenic radionuclides near the Oyster Creek reactor, and that there are ample grounds for further study to determine the exact levels and potential for harm from the reactor-released radionuclides.One thing that the variation clearly demonstrates is the insufficiency of the nuclear generating station's testing procedures. Oyster Creek uses a relatively modest annual sampling size, considering the scope of its operations. It annually reports a total of 40 water samples from four locations; sediment is collected only twice a year from four locations, and vegetation is collected only from three locations. The reactor's samples, while perhaps sufficient to show that radiation levels are below E.P.A. limits, are not nearly sufficient to determine the distribution of radionuclides, and thus cannot estimate the potential human and environmental harm. The variation between samples is often great, even for samples from the same location. In this study, for the sample sites where multiple samples were taken (on different testing days), the range of those data points from the same site encompassed an average of 25 percent of the entire spread of the data for that radionuclide in that region.

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More About This Resource...

This winning entry in the Museum's Young Naturalist Awards 2008 is from a Pennsylvania 12th grader. Anastasia conducted a spatial study of radioactivity in the waters near the Oyster Creek Nuclear Generating Station. Her essay includes:

an overview of the Oyster Creek Nuclear Generating Station and of radionuclides;

details about the materials, methods, and procedures she used for her spatial study of radioactivity in the waters near the reactor; and

the results of her investigation, which proved her hypothesis that higher levels of anthropogenic radionuclides can be found closer the reactor.

Teacher Tip

Supplement a study of biology with an activity drawn from this winning student essay.

Send students to this online article, or print copies of the essay for them to read.

Working alone in or small groups, have students research cobalt-60 and report on its hazards.